1. Field of the Invention
The present invention relates to an image reading apparatus capable of reading images of both sides of a document.
2. Description of the Related Art
Conventionally, there has been available an image reading apparatus that has a sequence to read images of both sides of a document by one document conveyance (one pass double side sequence) by being separately provided with a sensor that reads the image of the front side of the document and a sensor that reads the image of the back side of the document.
Examples of the image reading apparatus that executes the one pass double side sequence include an apparatus in which a memory for storing front side images and a memory for storing back side images are independently provided as disclosed in Japanese Patent Application Laid-Open No. 2006-191228. This image reading apparatus is structured so that the image data of the front and back sides is transmitted from the memories for the front side and back side to an image processing apparatus (hereinafter, referred to as controller) provided in an image forming apparatus.
However, the invention described in Japanese Patent Application Laid-Open No. 2006-191228 does not take into consideration a case where a long document (a document longer than the A3 size, for example, a document that is equal to or longer than 420 mm and equal to or shorter than 630 mm in the conveyance direction) is read.
That is, in many cases, the memory size of the image reading apparatus is a size capable of storing the image data of an A3-size document that is read with a maximum resolution (for example, 600 dpi). However, in the case of a long document, the read image cannot all be stored in the memory.
To cope with this problem, it is conceivable to increase the memory size to the size of a long document that is not usually used, for the double side reading of the long document. However, a more expensive memory is required, which increases the manufacturing cost.